If the quadratic equation x^2 + 6x + k = 0 has roots -2 and -4, what is the valu

Practice Questions

Q1
If the quadratic equation x^2 + 6x + k = 0 has roots -2 and -4, what is the value of k?
  1. 8
  2. 12
  3. 16
  4. 20

Questions & Step-by-Step Solutions

If the quadratic equation x^2 + 6x + k = 0 has roots -2 and -4, what is the value of k?
  • Step 1: Understand that the roots of the quadratic equation are the values of x that make the equation equal to zero.
  • Step 2: Identify the given roots, which are -2 and -4.
  • Step 3: Recall Vieta's formulas, which state that for a quadratic equation of the form ax^2 + bx + c = 0, the sum of the roots (r1 + r2) is equal to -b/a and the product of the roots (r1 * r2) is equal to c/a.
  • Step 4: Since the equation is x^2 + 6x + k = 0, we can see that a = 1, b = 6, and c = k.
  • Step 5: Calculate the product of the roots: (-2) * (-4) = 8.
  • Step 6: According to Vieta's formulas, the product of the roots is equal to c/a, which means k = 8 (since a = 1).
  • Step 7: Conclude that the value of k is 8.
  • Quadratic Equations – Understanding the standard form of a quadratic equation and how to find roots.
  • Vieta's Formulas – Using Vieta's relations to relate the coefficients of a polynomial to sums and products of its roots.
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